


a pair of dull scissors in the yellow light

by avosettas



Category: Undertale (Video Game)
Genre: Body Worship, Ecto-Penis (Undertale), Frottage, Horrorfell Sans (Undertale), Horrorfell Sans/Underswap Sans (Undertale), M/M, Praise Kink, Size Difference, Underswap Sans (Undertale)
Language: English
Status: Completed
Published: 2021-01-12
Updated: 2021-01-12
Packaged: 2021-03-16 10:21:46
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 1,522
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/28705095
Author URL: https://archiveofourown.org/users/avosettas/pseuds/avosettas
Summary: Rust has been dragging this on for far too long in Blue’s opinion, although if he’s being honest with himself, he doesn’t mind quite as much as he’s trying to convince himself he does.
Relationships: Sans/Sans (Undertale)
Comments: 3
Kudos: 48





	a pair of dull scissors in the yellow light

**Author's Note:**

  * For [armethaumaturgy](https://archiveofourown.org/users/armethaumaturgy/gifts).



> LMAO LITERALLY NONE OF THIS FELT SFW ENOUGH TO USE IN THE SUMMARY... maybe it's a Sign that i should start writing actual summaries instead of. copy pasting lines. 
> 
> anyway. something something i have barely written dicks ever and never written hf!sans i lov u goodnight

Rust has been dragging this on for far too long in Blue’s opinion, although if he’s being honest with himself, he doesn’t mind quite as much as he’s trying to convince himself he does.

“you’re so cute…” Rust mumbles, stroking his claws down Blue’s cheek. The scratching sensation does little to ease the ache in his pelvis, but Blue pushes up against his mate’s hand anyway. 

Sitting between Blue’s splayed legs, Rust has folded himself to cover his smaller mate, warm above him. Beneath him, Blue squirms, though there’s little room to move, caged by Rust as he is; mostly he’s wracked by full-body shivers, each rattling him and interrupting the rumble of Rust’s purr that’s been filling the entire room. 

Rust’s eyelights are intently focused on him, little pinpricks shining from the black of his eye sockets. It could be frightening - his left eye socket is marred, only the bottom rim remaining, while the rest disappears into the gaping hole in his skull. But Blue preens under the attention, because there’s nothing but love and dedication to him there. 

“Rust,” he says, though his jawbones feel slow and it sounds slurred.

“right here, darlin’,” Rust replies easily, one hand still on Blue’s face. The other traces the lines of his ribs, slowly so as to be less ticklish and more sensual. “...stars, you’re pretty… what d’you… what d’you need?” 

“Stop _teasing_ ,” Blue orders, but it’s very much a whine, and Rust chuckles. 

“i like it when you’re like this… desperate and… needy.” The hand on Blue’s face leaves, though it quickly reappears in his pelvis. Rust dips his claws into the misty cyan magic that’s been gathering there for stars-only-knows how long, wiggling them and making the loose magic ripple like water. “‘nd i like the shade of your magic…” 

Blue bucks into the indirect touch, biting his tongue to keep quiet, and Rust’s knuckles hit the rim of his ilium with the movement - his hand is so _big_ , his fist practically fills the whole of Blue’s pelvic inlet. Blue is not a small monster - he’s short, maybe, and a little on the stout side when he’s manifested his ecto-body, but his bones and such are a rather average size. 

Rust just happens to be huge, dwarfing Blue in every aspect. 

“do that again,” Rust tells him, swirling his forefinger in the cloud of magic. “and… stop muffling yourself. i like hearing you.” 

Blue flushes at that, though he does listen and stop biting his tongue - it was starting to hurt, anyway. Rust laughs above him, leaning down a bit to rest somewhat sprawled on Blue’s ribcage and the bed. “cute when you… when you blush. your magic… the color is pretty.” 

He crooks the finger in Blue’s pelvis, letting his claw scratch gently on his mate’s sacrum, and Blue arches and moans. “Rust, please -” 

“fine, i’ll stop teasin’,” Rust interrupts with his best exaggerated pout. His hand retreats and Blue rolls his hips, trying to follow it, until Rust moves up and murmurs, “form something nice for me,” against his neck. His jagged teeth catch on Blue’s cervical vertebrae, and that’s all it takes to make his magic manifest. 

Blue exhales shakily as Rust moves off of him, leaning back to stare from his place between Blue’s legs. In the meantime, Blue’s magic has taken his place, settling in from his knees to his floating ribs. His cock sits above his pelvis now, and Blue whimpers when the open air hits it, icy cold against his erection. 

“look a’ you,” Rust says, voice low. “could stare at you all day…” He sits back on his haunches, and the look in his eyelights is nothing short of hungry. Blue shivers, from both the cold of the room and Rust’s starving gaze. 

The chill doesn’t last long, though; Rust has taken the time to form his own ecto-body, though the magic wavers a bit around the edges and it’s not quite as bright a red as it should be. His hands are back on Blue as soon as he leans forward again, one pawing at his thigh, lifting it to rest on his own so he can move closer, the other wrapping loosely around Blue’s cock. From this close, the heat radiating off of Rust’s body is palpable, and Blue wants to go to it like a moth to a lantern. 

Rust hardly moves, barely twitching his fingers one after the other, but it’s enough for Blue in his frenzied state. The stimulation is clumsy, but his hand is big and warm, and it practically engulfs Blue’s hard-on. He laughs when Blue tries to thrust up into his hand. “not yet… soon. i like teasing you too much to… let this end so quickly.” Rust’s opposite hand moves to stroke Blue’s hip and belly, and he purrs at the soft pudge of the ecto-flesh there. “so soft…” 

“You’re so - ah - mean today,” Blue gasps, squirming as Rust moves the hand on his cock slightly. Rust smiles, satisfied with himself, as his other hand shifts lower to press his mate’s hip into the bed. 

“i like when you… when y’squirm,” Rust says, though he leans over and grabs the lube from their bedside table with the hand that’s not holding Blue’s dick. “but you’re real cute, ‘nd… you beg so sweet.” 

Blue whines when his hand moves, trying to thrust into the open air as Rust fiddles with the lube. He squirts a generous amount onto one palm, and then flips the cap shut and leaves the tube beside him on the bed. 

“Hurry up,” Blue mumbles, fisting his hands in the sheets as he watches Rust spread the lube onto his own fingers. 

“not very patient today,” Rust mumbles. “s’okay though, i’m gettin’ impatient too.” 

Instead of touching Blue, Rust uses the literal _glob_ of lube he’s collected on his hand to slick up his own cock, taking it in his hand and giving it a few firm strokes. Blue stares, and though he feels too aroused to really dwell on the shame, he knows his face must be a bright shade of cyan. 

Rust isn’t putting on a show, though; with his dry hand, he reopens the tube and squirts another generous helping of lube out. Then, he takes Blue’s dick in hand, the sudden cold of the puddled lubricant making him squeal. 

“sorry,” Rust snorts, though he doesn’t seem sorry. Blue accepts his apology when he leans up to press his fangs to Blue’s cheek, though. “...this shouldn’t be too cold.” 

Blue doesn’t have time to wonder what _this_ is before Rust has pressed himself as close to his mate as he can get, taking both their cocks in his slicked up hand. He gasps and squirms, but Rust holds him firm to the bed. “really sensitive,” Rust observes idly, letting his thumb glance along the weeping head of Blue’s cock.

Blue keens at the soft touch, and through the haze of arousal he can see that Rust positively dwarfs him this way, too. His hand covers most of Blue’s dick, even fisted around it and his own. And the head of Rust’s cock is easily visible above Blue’s; the one conscious thought he has is that he _wants it_.

He doesn’t realize that he’s spoken out loud until Rust speaks, breathily mumbling “not today, darlin’,” and Blue murmurs back incoherently as Rust traces around the head of his cock again. “neither o’ us have… the patience to stretch y’out today.” His chuckle is less a laugh and more a low growl-like noise, but Blue purrs softly in response anyway, rolling his hips into Rust’s hand. 

Rust purrs in response, the same low pitch as his laugh, and finally moves his hand. The friction is _delightful_ , and Blue arches against it so hard that he feels his back ache with the stretch. He hears Rust’s purr warble off into a laugh, and feels the press of his gentle claws on Blue’s ribs, pressing him into the bed as he moves ever closer. 

Rust fucks against him in earnest, dragging his cock and his hand against Blue at different, arrhythmic paces. Blue can only babble incoherently in response, held against the bed by Rust. 

“so good,” Rust gasps, gentle praises becoming messy gibberish, his movements becoming erratic and faster. “so soft ‘nd good for me…” 

The high-pitched noise Blue makes as he comes is slightly embarrassing, but he’s hardly sure Rust even notices it, still preoccupied with chasing his own orgasm. He tenses as Rust continues, and then comes a moment later, the red substance joining Blue’s cum on his hand. 

Blue sags into the bed, finally spent, and Rust droops a bit and then collapses next to him, stained hand thrown across Blue’s belly. “Rust, no,” Blue mumbles weakly. “We need to shower.” 

“nope,” Rust murmurs in reply, purring up a storm that makes Blue’s conjured belly tingle pleasantly. “g’nna snooze…” 

“Shower,” Blue insists weakly, but Rust is already asleep, draped halfway on top of him. He supposes he’ll just make Rust change the sheets when they get up. Eventually.

**Author's Note:**

> twitter @avosettas


End file.
